Taking a hydraulic power shovel type excavator as an example of construction machines, as well known in the art, a hydraulic pump is driven by an engine to supply pressurized oil from the hydraulic pump to hydraulic cylinders and hydraulic motors as actuators in various operating parts of the machine, which are operated by way of control levers or other operation control means manipulated by an operator who is seated within an operating room or cab of the machine.
Normally, a variety of instruments are mounted in the cab to let an operator recognize operating conditions of the machine. For example, the instruments in the cab include an engine speedometer, fuel indicator, cooling water temperature indicator, operating oil temperature indicator and hour meter. In this regard, it is more rational to display readings of various instruments collectively at a prominent place rather than using separately mounted indicators, which would scatter the operator's attention. With recent price down and improvements in accuracy as a display device, liquid crystal displays have been favorably adopted and put in use as a monitor screen which displays various operating conditions of a machine and other necessary information collectively by way of color images. By the introduction of a monitor display of this sort, it has become possible to put various information on a monitor screen in a compact and easily recognizable form, permitting an operator to grip current operating conditions of a machine accurately.    Patent Literature 1: Japanese Laid-Open Patent Application H11-81393